revert: explicitly track added but deleted file Added + deleted file are files that need to be untracked from the dirstate but that are already missing on disk. The current `_performrevert` code is handling that with exception catching. We will be able to do better with a dedicated set.

revert: have an explicit action for "forget" The distinction between "remove" and "forget" used to be in special logic checking for the state of the file in the dirstate. Now that we have dedicated filtering, we can stop relying on this logic and have two distinct actions.

revert: split between newly added file and file added in other changeset These two kinds of files are handled differently. One is deleted and the other is just forgotten (the file is untracked but left in place). The distinction is done in the `_performrevert` code itself and we would like to get ride of this.